The present invention concerns food products with a fibrous texture, obtained mainly from whey proteins, a manufacturing process by extrusion baking of these products and a manufacturing installation for application of the process.
Processes for the manufacture of dairy products by continuous extrusion are already known.
Document EP-A-727 138 describes one such extrusion process by means of which cheese or cheese products are obtained from a curd or milk fraction resulting from ultrafiltration of milk. The process is comprised of the following stages: introduction of raw materials, transfer into a barrel with at least one zone in which the temperature is between 60xc2x0 and 120xc2x0 C. involving blending, texturing and baking. This process gives rise to products with stretched structures whose fibres have a diameter that is generally greater than 0.1 mm and in the order of millimeters.
Document WO-96/34 539 describes a process used to obtain a textured protein matrix containing a dispersion of inclusion bodies. These products are obtained by means of a high-temperature extrusion process, notably at temperatures of 125 to 160xc2x0 C. High temperatures such as this lead to the destruction of the initial protein mixture. The products obtained include protein fibres which are stable after cooling. This document essentially describes the use of vegetable proteins such as soya.
Document WO-96/25051 describes a process for the manufacture of a soft or semi-soft fibrous cheese. The fibrous mass is obtained after extrusion of the curdled milk. These processes do not allow a cheese or milk mixture to be used to obtain a product with an extremely fine fibrous structure, comprising fibres whose sizes are in the range of xcexcm to 0.1 mm, noticeable when the product is chewed and conferring on it original organoleptic characteristics.
Document U.S. Pat. No. 4,156,028 also describes a process for the manufacture of fibre products whose fibres have diameters in the order of 100 xcexcm for example. However, these products are obtained by a technique which involves dissolution followed by a coagulation bath; the principles and materials of this technique are considerably different from extrusion baking which brings together specific pressure and temperature features. The products obtained do not have a ramified network structure such as that described below.
The present invention concerns food products with a fibrous texture, obtained mainly from whey proteins, a manufacturing process by extrusion baking of these products and a manufacturing installation for application of the process. A first aspect of the invention proposes a product obtained by extrusion baking of a mixture of dairy or cheese origin. This product has a fibrous structure with a network of macroscopic fibres whose diameters are in the order of 0.1 mm to 1 mm, ramified into microscopic fibres with diameters in the order of 1 xcexcm to 0.1 mm, the dry matter in the product being at least partially obtained from whey. The dry matter in the product typically comprises 30% to 100% of dry matter originating from whey. The product consists of 15 to 50% of dry matter and typically 25 to 40%. The dry matter of the product consists of at least 35% of total proteins. The dry matter originating from whey includes isolated and/or concentrated proteins, and/or dried whole whey, and/or dried whey fractions such as lactose, milk fats, lactoferrin, calcium or other milk minerals or fractions.
According to a second aspect, the invention concerns a food preparation incorporating a product in keeping with the description above added to various ingredients chosen from among cheeses, milk and derivative products (yoghurt, milk cream, milk powder, fromage blanc, butter), cereals, starches, flour, semolina, fruits and dried fruits, spices, seasoning, fats, flavouring, sugar-containing ingredients (sugar, honey), pieces of meat or fish or vegetables, so as to form ready-made meals, children""s snacks, sandwiches, snack foods, breakfast products, burger- or sausage-shaped cheese products, vegetarian products, spreads, pate and cooking ingredients.
According to a third application, the invention concerns a process for the manufacture of products with a fibrous structure comprised of the following steps:
a) introduction of raw materials containing whey proteins into an extruder with at least one screw;
b) transfer of raw materials from one end to the other of the extruder barrel, adjusting the screw(s) and temperature within the barrel such that raw materials successively undergo a mixing and heating step up to a temperature of about 130xc2x0 C., followed by a melting step with an increase in temperature of the material to above 130xc2x0 C., generally between 140xc2x0 C. and 200xc2x0 C., and an increase in pressure to between 0 and 50 bars, such that plasticization of the transferred material takes place, especially of whey proteins;
c) extrusion at the far end of the barrel of the material obtained after plasticization through a die adapted for texturization, shaping and cooling the material such that a product with a fibrous structure is obtained.
The process also includes a cutting step at the outlet of the die. According to one application, it includes a step where the product is dried at the outlet of the die after cutting to produce rehydratable fibres for food preparations if need be. It can also include a shaping step comprised of mechanical forming processes using a shaper or moulds or piping followed by pasteurisation and slicing, with, the products obtained undergoing at least one of the following steps: decoration, coating, stamping, filling, frying, baking, pasteurisation, sterilisation, packaging.
According to a fourth aspect, the invention concerns a manufacturing installation for the application of the process presented above comprised of a screw extruder with two very similar interlocking screws which rotate in the same direction or in the opposite direction inside a horizontal barrel, a filling device attached at the near end of the barrel, fitted with one or more metering devices for metered flow of the mixture at a predetermined rate, an extrusion die located at the far end of said barrel, thermal treatment assembly for fine-tuning the temperature within the barrel and extrusion die, said barrel being comprised of:
(a) a first zone for supply of the product formula;
(b) a second zone for mixing, moisturisation where this is required, and heating the material up to a core temperature of at least 130xc2x0 C.;
(c) a third zone for melting, increasing the temperature of the material to over 130xc2x0 C., generally between 140 and 200xc2x0 C. and pressure of the material to between 0 and 50 bars, depending on the composition of the formula, in which protein plasticization takes place, especially of whey proteins. Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.